The reading of electrical energy has historically been accomplished with human meter readers that came on-site to the customers' premises and manually documented the readings. The information extracted from the meters was simple pulse initiator information of basic quantities. (A pulse initiator (PI) is an optical device that picks up the rotations of a disc on an electromechanical meter. The disc rotations, which are proportional to energy use, are converted by the PI into pulses that can be read by computing devices.) Over time, manual meter reading has been enhanced with walk-by or drive-by reading systems that utilize radio communications between the meters and a meter reading device. The information that these walkby and driveby systems collected increased, but still the functions provided by the communication systems were limited. More recently, over the last few years, there has been a concerted effort to accomplish meter reading by installing fixed networks that would allow data to flow from the meter to a host computer system without human intervention.
In general, fixed communication networks can operate using wire line or radio technology. Distribution line carrier systems are wire based and utilize the utility's lines for communications. These systems typically use a single frequency channel and allow the impedance and transfer characteristics of the transformers in the substation to prevent injection equipment in one station from interfering with receivers in another station. This built-in isolation in the network makes time division multiplexing less critical than for radio based metering systems. Further background information regarding AMR (also called network meter reading, or NMR) can be found in U.S. Pat. No. 4,056,107, Feb. 15, 1990, "Radio Communication Network For Remote Data Generating Stations." Further information regarding the use of a meter having repeating capability in a CEBus network may be found in U.S. patent application Ser. No. 08/828,539, filed Mar. 31, 1997, "Communications Module Based Repeater".
Radio frequency (RF) technology has recently tended to be the solution of choice due to its higher data rates and independence of the distribution network. RF frequencies approaching a gigahertz can be unlicensed or licensed, but unlicensed systems are significantly restricted in power output. This power restriction coupled with typical RF problems of attenuation, fading, noise and reflections makes some sites in a fixed network very inaccessible to a central node, and thus it can be difficult to achieve two-way performance adequate for the desired functions. These problems are sometimes resolved by manually reading the hard to access sites or by adding a vehicle system to the fixed network system (see, e.g., U.S. Pat. No. 5,495,239, Feb. 27, 1996, "Method and Apparatus for Communicating with a Plurality of Electrical Metering Devices and a System Control Center with a Mobile Node").